Abstract
AbstractMyelination by oligodendrocytes is critical for fast axonal conduction and for the support and survival of neurons in the central nervous system. Recent studies have emphasized that myelination is plastic and that new myelin is formed throughout life. Nonetheless, the mechanisms that regulate the number, length, and location of myelin sheaths formed by individual oligodendrocytes are incompletely understood. Previous work showed that lysosomal transcription factor TFEB represses myelination by oligodendrocytes and that the RagA GTPase inhibits TFEB, but the step or steps of myelination in which TFEB plays a role have remained unclear. Here, we show that TFEB regulates oligodendrocyte differentiation and also controls the number and length of myelin sheaths formed by individual oligodendrocytes. In the dorsal spinal cord oftfebmutants, individual oligodendrocytes produce fewer myelin sheaths, and these sheaths are longer than those produced by wildtype cells. Transmission electron microscopy shows that there are more myelinated axons in the dorsal spinal cord oftfebmutants than in wildtype animals, but no significant change in axon diameter. In contrast totfebmutants, oligodendrocytes inrragamutants produce shorter myelin sheaths. The sheath length inrraga; tfebdouble mutants is not significantly different from wildtype, consistent with the antagonistic interaction between RagA and TFEB. Finally, we find that the GTPase activating protein Flcn and the RagCa and RagCb GTPases are also necessary for myelination by oligodendrocytes. These findings demonstrate that TFEB coordinates myelin sheath length and number during myelin formation in the central nervous system.Graphical Abstract
Publisher
Cold Spring Harbor Laboratory